1. The Field of the Invention
The present invention relates generally to the control and reduction of electromagnetic interference (“EMI”). More particularly, some example embodiments relate to EMI containment structures that can be employed to at least partially contain EMI generated by optical subassembly (“OSA”) components within the OSA.
2. The Relevant Technology
Computing and networking technology have transformed our world. As the amount of information communicated over networks steadily increases, high speed transmission becomes ever more critical. Many high speed data transmission networks rely on optical transceivers and similar devices for facilitating transmission and reception of digital data embodied in the form of optical signals over optical fibers. Optical networks are thus found in a wide variety of high speed applications ranging from modest Local Area Networks (“LANs”) to backbones that define a large portion of the infrastructure of the Internet.
Typically, data transmission in such networks is implemented by way of an optical transmitter (also referred to as an “electro-optic transducer”), such as a laser or Light Emitting Diode (“LED”). The optical transmitter emits light when current is passed through it, the intensity of the emitted light being a function of the magnitude of the current. Data reception is generally implemented by way of an optical receiver (also referred to as an opto-electric transducer), an example of which is a photodiode. The optical receiver receives light and generates a current, the magnitude of the generated current being a function of the intensity of the received light.
Various other components are also employed by the optical transceiver to aid in the control of the optical transmit and receive components, as well as the processing of various data and other signals. For example, the optical transmitter is typically housed in a transmitter optical subassembly (“TOSA”), while the optical receiver is housed in a separate receiver optical subassembly (“ROSA”). The transceiver also typically includes a driver (e.g., referred to as a “laser driver” when used to drive a laser signal) configured to control the operation of the optical transmitter in response to various control inputs and an amplifier (e.g., often referred to as a “post-amplifier”) configured to amplify the received signal prior to further processing. A controller circuit or controller controls the operation of the laser driver and post-amplifier.
One common difficulty associated with transceiver modules is the generation of EMI. The generation of EMI by a module is a matter of concern because such EMI can seriously impair, if not prevent, the proper operation of other systems and devices in the vicinity. In recognition of the problems presented by EMI generation, various attempts have been made to control and/or contain EMI. Many such attempts have focused on the development of various types of structures intended to contain, to the extent practicable, the signals and/or structure that generate EMI. However, the problems and deficiencies inherent in such attempts have become increasingly problematic as data rates and corresponding operational frequencies increase.
For example, some attempts at EMI control have focused on the use of stamped sheet metal parts bent or folded to define a Faraday cage for the control of EMI. However, an inherent limitation of such approaches is that mechanical reliefs, such as holes or punchouts, are provided in order to enable the bending of the metal into the desired shape or to provide some type of connection between the components inside the faraday cage and components outside of the cage. Unfortunately, such holes or punchouts provide an escape path for EMI.
Further, many devices such as transceivers and transponders are ‘pluggable.’ Pluggable devices, for example, may include an edge connector that can be removably plugged into a corresponding connector of another device, such as a host board. Such host boards often include some type of EMI control cage structure within which the device is positioned when it has been plugged into the host board. However, typical cages and similar structures are problematic because they generally fail to completely and reliably enclose the portions of the pluggable device, such as the edge connector for example. This then becomes one area where EMI can escape.
This problem is further complicated by the fact that components such as optical transceivers typically interface with optical fibers using ports. Optical signals are transmitted through and received from optical fibers via the ports. Unfortunately, these ports provide a path through which EMI can escape. This is true even when the ports are connected with optical fibers in conventional devices.
The subject matter claimed herein is not limited to embodiments that solve any disadvantages or that operate only in environments such as those described above. Rather, this background is only provided to illustrate one exemplary technology area where some embodiments described herein may be practiced